Spotting any strange object in a photo from Mars will generate a huge amount of interest from scientists, the media and public alike, but it seems the strange "light source" seen in one of Mars rover Curiosity's landscape observations has two possible rational, yet fascinating, explanations.

In a NASA news release late on Tuesday, a member of the team that built and operates the rover's Navigation Camera (Navcam) outlined the most likely causes of the bright dot - a feature that isn't all that rare in Curiosity's raw imagery beamed back to Earth.

"In the thousands of images we've received from Curiosity, we see ones with bright spots nearly every week," said Justin Maki of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "These can be caused by cosmic-ray hits or sunlight glinting from rock surfaces, as the most likely explanations."

This official word builds on the preliminary theories as to what the bright dot is in a photo taken on Sol 589 (April 3) of Curiosity's mission.

Cosmic ray hits are all too familiar in observations acquired by space instrumentation. Even on the surface of Mars, high-energy particles can penetrate deep into the thin atmosphere, causing hot spots on robotic camera CCDs. It just so happened that this particular bright spot sits above the Martina landscape, adding to the impression that it is a real light-emitting phenomenon.

But there's an even more exciting possibility, as Maki points out. The light could be a reflection from a particularly shiny rock surface, as the bright light has been spotted in approximately the same location on two different days at around the same time in the day.

By the reckoning of Curiosity's mission scientists, the location of the possible shiny rock was around 160 meters from the rover's April 3 position.

The rover's Navcam is composed of two different cameras (a left ‘eye' and a right ‘eye') that can provide stereo views of the Martian surface. Usually any strange objects that are detected appear in both cameras, making the identification of anything weird fairly easy. But the April 2 and April 3 detections were made through the right camera only.

"Normally we can quickly identify the likely source of a bright spot in an image based on whether or not it occurs in both images of a stereo pair," added Maki. "In this case, it's not as straightforward because of a blocked view from the second camera on the first day."

No doubt NASA will continue investigating this fascinating phenomenon and if it does prove to be a particularly shiny Mars rock glinting in the sunlight, it will be interesting to see whether mission managers decide to investigate further.